WO2011054257A1 - 一种优化媒体路径的建立方法和实现该方法的信令网关 - Google Patents

一种优化媒体路径的建立方法和实现该方法的信令网关 Download PDF

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Publication number
WO2011054257A1
WO2011054257A1 PCT/CN2010/078009 CN2010078009W WO2011054257A1 WO 2011054257 A1 WO2011054257 A1 WO 2011054257A1 CN 2010078009 W CN2010078009 W CN 2010078009W WO 2011054257 A1 WO2011054257 A1 WO 2011054257A1
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Prior art keywords
alg
sdp
session
response
sdp response
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PCT/CN2010/078009
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English (en)
French (fr)
Inventor
谢振华
郝振武
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中兴通讯股份有限公司
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Application filed by 中兴通讯股份有限公司 filed Critical 中兴通讯股份有限公司
Priority to CA2780182A priority Critical patent/CA2780182C/en
Priority to US13/504,546 priority patent/US9281964B2/en
Priority to BR112012010625A priority patent/BR112012010625A8/pt
Priority to EP10827871.4A priority patent/EP2485444B1/en
Priority to JP2012535608A priority patent/JP5506941B2/ja
Publication of WO2011054257A1 publication Critical patent/WO2011054257A1/zh

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/66—Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/64—Hybrid switching systems
    • H04L12/6418—Hybrid transport
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/10—Architectures or entities
    • H04L65/1016—IP multimedia subsystem [IMS]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/10—Architectures or entities
    • H04L65/102—Gateways
    • H04L65/1033—Signalling gateways
    • H04L65/104—Signalling gateways in the network
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/1066—Session management
    • H04L65/1101—Session protocols
    • H04L65/1104—Session initiation protocol [SIP]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/02—Topology update or discovery

Definitions

  • the present invention relates to the field of mobile communication technologies, and in particular, to a method for establishing an optimized IMS media path and a signaling gateway implementing the method.
  • IP Multimedia Core Network Subsystem is an IP-based network architecture proposed by the 3rd Generation Partnership Project (3GPP), which is an open system.
  • 3GPP 3rd Generation Partnership Project
  • a flexible business environment that supports multimedia applications and provides users with rich multimedia services.
  • the IMS can be divided into a control layer and a service layer.
  • the control layer mainly includes a session control function (Call Session Control Function, referred to as CSCF) for service triggering and control, and the CSCF can be further divided into a proxy CSCF (Proxy CSCF, abbreviated as follows).
  • CSCF Session Control Function
  • proxy CSCF Proxy CSCF, abbreviated as follows.
  • query CSCF Interrogating CSCF, referred to as I-CSCF
  • CSCF Server CSCF, S-CSCF for short
  • the service layer mainly includes a series of application servers (Application Servers, AS for short), which are used to provide specific service services.
  • the ASs can be independent entities or exist in the S-CSCF.
  • the operation mode is as follows:
  • the control layer (S-CSCF) controls the service trigger according to the subscription information of the user, invokes the service on the AS, and implements the service function.
  • gateway devices for processing IMS signaling and media in the IMS network, such as the P-CSCF and its controlled Access Gateway (AGW), and the interactive border control function (Interworking Border Control).
  • I-BCF Inter Border Gateway
  • SBC Session Border Control
  • ALG Application Layer Gateway
  • TrGW Transmit Gateway
  • the gateway devices that handle IMS signaling and media are collectively referred to as signaling media gateways.
  • the P-CSCF and AGW can be considered as one signaling media gateway.
  • the origin of the call setup request or the call update request is referred to as the near end of the media gateway, and is referred to as the far end of the media gateway.
  • the protocol for negotiating the media resource information in the IMS system is the Session Description Protocol (SDP).
  • SDP Session Description Protocol
  • the interaction mode of the protocol is Request response mode, that is, an SDP request must have an SDP response (unless an error is rejected)
  • the content of the SDP request and response is media resource information
  • the media resource information includes media owner information (including address information), media connection address Media type and media port and codec information related to the media type.
  • the number, type and order of media must be exactly the same as the number, type and order of media in the SDP request.
  • the content of the SDP protocol is carried by the message body of the Session Initiation Protocol (SIP) message.
  • SIP Session Initiation Protocol
  • the interaction process is independent of the SIP request response mode. That is, the SIP request or response message can carry the SDP request, and can also carry the SDP. In response, you may not carry the SDP protocol content.
  • FIG. 1A is a schematic diagram of an existing setup and optimized IMS media path, and describes different media paths and corresponding signaling paths between the IMS terminal UE-A and the IMS terminal UE-B.
  • the media paths established by the existing call process are: UE1, TrGW1, TrGW2, TrGW3, TrGW4a, UE2, and the optimized media paths are: UE1, TrGWlb, TrGW5, TrGW4b, UE2, optimized
  • the media path is shorter than the unoptimized media path, and one TrGW is missing, so the optimized media path is more resource efficient and more efficient.
  • the signaling gateway ALG1 controls TrGWla and TrGWlb
  • ALG2 controls TrGW2
  • ALG3 controls TrGW3, ALG4 controls TrGW4a and TrGW4b
  • ALG5 controls TrGW5.
  • FIG. 1B is a flow chart of establishing an optimized IMS media path, which corresponds to the schematic diagram of FIG. 1A, and mainly includes the following steps:
  • Step 101 UE1 sends an SDP request to UE2 to negotiate media resource information, for example, by sending SIP call signaling, that is, an INVITE request, or an update signaling, that is, a relNVITE request, with the SIP request message.
  • SIP call signaling that is, an INVITE request
  • update signaling that is, a relNVITE request
  • the body carries the SDP request, and the content of the SDP request is Media resource information of UE1;
  • Step 102 The SDP requests to reach the signaling gateway ALG1, and the signaling gateway ALG1 selects TrGW1 as the media gateway, controls the media gateway to use the media resource information in the SDP request, and allocates the media resource for connecting to the remote end, and the ALG1 uses the TrGWla.
  • the media resource information of the remote connection is used to replace the media resource information in the SDP request, and then the related information of the ALG1 and the information related to the session identifier are added to the SDP request to forward the SDP request, for example, by forwarding the SIP signaling to carry the SDP request.
  • Step 103 The SDP request arrives at the signaling gateway ALG2, and the ALG2 selects the TrGW2 as the media gateway, controls the media gateway to use the media resource information in the SDP request, and allocates the media resource for connecting to the remote end, and the ALG2 uses the TrGW2 for connecting the far
  • the media resource information of the terminal is used to replace the media resource information in the SDP request, and then the related information of the ALG2 and the information related to the session identifier are added to the SDP request to forward the SDP request, for example, by forwarding the SIP signaling to carry the SDP request for forwarding;
  • Step 104 The SDP requests to reach the signaling gateway ALG3, and the ALG3 selects the TrGW3 as the media gateway, controls the media gateway to use the media resource information in the SDP request, and allocates the media resource for connecting to the remote end, and the ALG3 uses the TrGW3 for connecting the far
  • the media resource information of the end is used to replace the media resource information in the SDP request, and then the related information of the ALG3 and the session identifier are added to the SDP request, and then the SDP request is forwarded, for example, by forwarding the SIP signaling to carry the SDP request.
  • Step 105 The SDP requests to reach the signaling gateway ALG4, and the ALG4 selects the TrGW4a as the media gateway, controls the media gateway to use the media resource information in the SDP request, and allocates the media resource for connecting to the remote end, and the ALG4 uses the TrGW4a for connecting the far
  • the media resource information of the end is used to replace the media resource information in the SDP request, and then the related information of the ALG4 and the session identifier are added to the SDP request, and then the SDP request is forwarded, for example, by forwarding the SIP signaling to carry the SDP request, and forwarding.
  • the SDP request finally arrives at UE2;
  • Step 106 The UE2 uses the media resource information in the SDP request to negotiate, and then sends an SDP response, and carries the media resource information of the UE2, for example, a "200 OK" response by using the SIP signaling, and the message body of the SIP response carries the SDP response. , the SDP response arrives at ALG4;
  • Step 107 ALG4 determines ALG4 according to each ALG related information on the received path. There is a shorter path between ALG1, and then a SIP negotiation request message is sent to ALG1 to establish a second media path segment, and carries some received ALG1 related information, such as sending an INVITE message without an SDP request, the target of the message. The address of the ALG1, and carrying the session identification information provided by ALG1, the SIP signaling will create a new session signaling channel;
  • Step 108 The SIP negotiation request message is routed to the ALG5, and the ALG5 forwards the message to
  • Step 109 The SIP negotiation request message arrives at ALG1, and the ALG1 selects TrGWlb as the media gateway (can be selected according to the negotiation request message), allocates the media resource for connecting to the remote end, and associates the media negotiation twice, ALG1
  • the SDP request is generated by the TrGWlb for connecting the remote media resource information, and the SDP request is sent to negotiate the media resource information, for example, by sending a "200 OK" response of the SIP signaling, and the message body of the SIP response carries the SDP request.
  • Step 110 The SDP request arrives at the signaling gateway ALG5, and the ALG5 selects the TrGW5 as the media gateway, controls the media gateway to use the media resource information in the SDP request, and allocates the media resource for connecting to the remote end, and the ALG5 uses the TrGW5 for the connection.
  • the remote media resource information replaces the media resource information in the SDP request, and then forwards the SDP request, for example, by forwarding the SIP signaling to carry the SDP request for forwarding, and the forwarded SDP request finally reaches ALG4;
  • Step 111 The ALG4 decides to select the second media path segment, and then selects the TrGW 4b as the media gateway, controls the media gateway to use the media resource information in the SDP request, and allocates the media resource for connecting to the remote end, and the ALG4 uses the TrGW4b for connecting.
  • the remote media resource information replaces the media resource information in the SDP request, and then forwards the SDP request, for example, the message body of the UPDATE (update) request by the SIP signaling carries the SDP request, and the forwarded SDP request finally arrives at the UE2;
  • Step 112 The UE2 receives the new SDP request, updates to use the media resource information in the SDP request, and sends an SDP response to the ALG4.
  • the SDP response content is the media resource information of the UE2, for example, the "200 OK" response through the SIP signaling. Transmitting the SDP response with the message body of the SIP response, and the SDP response arrives at ALG4;
  • Step 113 The ALG4 generates an SDP response by using the media resource information of the TrGW4b, and sends the SDP response to the ALG5, for example, by sending an ACK (Acknowledgement) request of the SIP signaling, and carrying the SDP response by the message body of the SIP request;
  • ALG1 controls TrGWlb to use the media resource information in the SDP response;
  • Step 115 At the same time as step 113, the ALG4 generates an SDP response carrying the invalid media resource information to indicate release of the media gateway allocated on the original session signaling channel, for example, setting the port number of the media to 0, and sending the original session signaling channel.
  • the SDP response for example, by sending a "200 OK" response of the SIP signaling, carrying the SDP response with the message body of the SIP response;
  • Steps 116-117 the SDP responses respectively reach ALG1 through ALG3 and ALG2, and ALG3, ALG2, and ALG1 release the media gateways allocated on the original session signaling channel, namely TrGW3, TrGW2, and TrGWla;
  • step 118 the ALG1 controls the TrGWlb to allocate the media resource information, and replaces the media resource information in the SDP response in step 117 with the media resource information, and then forwards the SDP response, for example, by forwarding the SIP signaling to carry the SDP response for forwarding, forwarding.
  • the SDP response eventually arrives at UE1.
  • the optimized media path is established, and the media path is UE1, TrGWlb, TrGW5,
  • TrGW4b TrGW4b, UE2.
  • the technical problem to be solved by the present invention is to provide a method for establishing an optimized media path and a signaling gateway implementing the method, which effectively shortens the call setup time.
  • the present invention provides a method for establishing an optimized media path, which is used in an IMS network, and the method includes:
  • the ALG determines that there is an optimized media path between the ALG and the second ALG, and sends the indication information in the sent SDP response when the SDP response of the first session is sent;
  • the first ALG sends an SDP request targeting the second ALG; After receiving the SDP response of the first session carrying the indication information, or after receiving the SDP request targeting the second ALG and the SDP response of the first session carrying the indication information, , Send the SDP response of the first session.
  • the indication information is used to indicate that an optimized media path is established with the second ALG, and the SDP response of the first session sent by the first ALG and the second ALG further carries resource information for establishing an optimized media path.
  • the indication information in the SDP response of the first session carries an association identifier, where the first ALG sends an SDP request targeting the second ALG, in the SIP message carrying the SDP request. Carrying the associated identifier.
  • the method further includes: after the second ALG receives the SDP request targeting the second ALG, initiating release of the first session media path resource.
  • the indication information includes information related to the second ALG.
  • the present invention also provides another method for establishing an optimized media path, which is used in an IMS network, and the method includes:
  • the ALG determines that there is an optimized media path between the ALG and the second ALG, and carries the indication information in the sent SDP response when sending the SDP response of the first session;
  • the second ALG After receiving the SDP response of the first session carrying the indication information, the second ALG sends an SDP request with the first ALG as a target.
  • the indication information is used to indicate that an optimized media path is established with the second ALG, the method further comprising:
  • the second ALG After receiving the SDP response of the first session carrying the indication information, the second ALG sends an SDP response of the first session, where the sent SDP response carries resource information for establishing an optimized media path.
  • the method further includes: after the first ALG receives the SDP request targeting the ALG, sending an SDP response of the second session; after receiving the SDP response of the second session, the second ALG initiates the first session media The release of path resources.
  • the indication information includes information related to the first ALG and the second ALG related Information.
  • the present invention also provides an ALG for establishing an optimized media path, comprising: a cut-out module and a cut-in module, wherein:
  • the cut-out module is configured to: during the process of forwarding the SDP request and the response, when receiving the SDP response of the first session, determining that an optimized media path exists between the ALG and another ALG on the first session media path, And transmitting the indication information in the sent SDP response when sending the SDP response of the first session; and sending an SDP request targeting the another ALG;
  • the hand-in module is configured to: after receiving an SDP response of the first session carrying the indication information related to the ALG, or receiving an SDP request targeting the ALG and carrying the indication information related to the ALG After the SDP response of a session, the SDP response of the first session is sent.
  • the SDP response of the first session forwarded by the cutting module and the SDP request carry an association identifier.
  • the SDP response of the first session sent by the cutting module and the hand-in module also carries resource information for establishing an optimized media path.
  • the ALG further includes an intermediate module, configured to: after receiving the SDP response carrying the first session unrelated to the ALG, send an SDP response of the first session carrying the indication information unrelated to the ALG.
  • the present invention further provides another ALG for establishing an optimized media path, comprising: a cut-out module and a hand-in module, wherein: the cut-out module is configured to: receive the first session during the process of forwarding the SDP request and the response When the SDP response is sent to determine that there is an optimized media path with another ALG on the first session media path, the SDP response is sent in the sent SDP response when the SDP response of the first session is sent;
  • the hand-in module is configured to: after receiving the SDP response of the first session carrying the indication information related to the ALG, send an SDP request with the ALG indicated by the indication information that the optimized media path exists between the ALGs.
  • the hand-in module is further configured to: after receiving the SDP response of the first session that carries the indication information related to the ALG, send the SDP response of the first session, and send the SDP response;
  • the SDP response of the first session sent by the cutting module and the hand-in module also carries resource information for establishing an optimized media path.
  • the cut-out module is further configured to: after receiving the SDP request targeting the ALG, send the SDP response of the second session;
  • the hand-in module is further configured to: after receiving the SDP response of the second session, initiate release of the first session media path resource.
  • the ALG further includes an intermediate module, configured to: after receiving the SDP response of the first session carrying the indication information unrelated to the ALG, send an SDP response of the first session carrying the indication information unrelated to the ALG.
  • FIG. 1A is a schematic diagram of an existing established optimized IMS media path
  • FIG. 1B is a flow chart of establishing an optimized IMS media path
  • Figure 2 is a flow chart of the first embodiment
  • Figure 3 is a flow chart of the second embodiment
  • the inventive idea of the present invention is to shorten the setup time by actively initiating a call.
  • the method of the invention comprises:
  • the first signaling gateway determines that there is optimized media between the second ALG and the second ALG.
  • the path when transmitting the SDP response of the first session, carries the indication information in the sent SDP response; b) the first ALG sends an SDP request targeting the second ALG;
  • the second ALG receives the SDP response of the first session carrying the indication information, or receives an SDP request targeting the second ALG and an SDP of the first session carrying the indication information After the response, the SDP response of the first session is sent.
  • the SDP response of the sent first session carries resource information for optimizing the media path. Sending an SDP response of the first session to complete establishment of the first session or update of the first session;
  • the second ALG After receiving the SDP request targeting the second ALG, the second ALG initiates release of the first session media path resource.
  • the second ALG After receiving the above SDP request targeted by itself, the second ALG sends an SDP response in the second session to complete the establishment of the second session.
  • the indication information in the SDP response of the first session carries an association identifier, and when the first ALG sends an SDP request targeting the second ALG, the session initiation protocol (SIP) carrying the SDP request
  • SIP session initiation protocol
  • the message carries the association identifier; the second ALG associates the first session and the second session according to the association identifier.
  • the indication information is used to indicate that the optimized media path to be established is related to the second ALG, and mainly includes information related to the second ALG, such as the location of the media gateway controlled by the second ALG, or the media including the first session. Sequence number information in the path.
  • step a After performing step a), perform the following steps:
  • the second ALG sends an SDP request to the first ALG after receiving the SDP response of the first session carrying the indication information.
  • the SDP response of the first session is forwarded to complete the establishment or update of the first session; the SDP response is carried for optimization. Resource information for the media path.
  • the first ALG sends an SDP response of the second session to complete establishment of the second session.
  • the second ALG initiates release of the first session media path resource.
  • the indication information is used to indicate that an optimized media path is established between the first ALG and the second ALG, and mainly includes information related to the first ALG and information related to the second ALG.
  • the ALG-related information may be, for example, location information of an ALG-controlled media gateway.
  • a signaling gateway it may be either the first signaling gateway or the second signaling gateway.
  • one signaling gateway may serve as the first signaling gateway and the second signaling gateway at the same time. Therefore, all functions of the first signaling gateway should also have all the foregoing second signaling gateway. The function.
  • a signaling gateway for implementing the foregoing method includes: a cut-out module and a cut-in module, where: the cut-out module is configured to receive a first session in a process of forwarding a Session Description Protocol (SDP) request and response When the SDP responds, it is determined that if there is an optimized media path between an ALGx on the first session media path, when the SDP response of the first session is forwarded, the SDP response carries the indication information; and is used for sending the ALGx SDP request for the target;
  • SDP Session Description Protocol
  • the hand-in module is configured to: after receiving an SDP response of the first session carrying the indication information related to the ALG, or receiving an SDP request targeting the ALG and carrying the instruction information related to the ALG After the SDP response of a session, the SDP response of the first session is forwarded.
  • the signaling gateway may also be another signaling gateway on the path between the first signaling gateway and the second signaling gateway.
  • the signaling gateway may further include an intermediate module, configured to receive the bearer and have nothing to do with the ALG. After the SDP response of the first session, an SDP response of the first session carrying the indication information unrelated to the ALG is sent.
  • Another signaling gateway that implements the foregoing method includes: a cut-out module and a hand-in module, where: the cut-out module is configured to receive a first session during a process of forwarding a Session Description Protocol (SDP) request and response In the SDP response, when it is determined that there is an optimized media path between the ALGx and the ALC, the SDP response carries the indication information when forwarding the SDP response of the first session;
  • SDP Session Description Protocol
  • the hand-in module is configured to send an SDP request to the ALGx indicated in the indication information after receiving the SDP response of the first session carrying the indication information.
  • the signaling gateway may also be another signaling gateway on the path between the first signaling gateway and the second signaling gateway.
  • the signaling gateway may further include an intermediate module, configured to receive the bearer and have nothing to do with the ALG. After the SDP response of the first session, an SDP response of the first session carrying the indication information unrelated to the ALG is sent.
  • FIG. 2 is a flowchart corresponding to the embodiment of FIG. 1A.
  • the UE1 establishes a call with the UE2, and includes a multiple session establishment process, which mainly includes the following steps:
  • Steps 201 to 206 are the same as steps 101 to 106 in FIG. 1B;
  • Step 207 The ALG4 receives the SDP response, and the ALG4 controls the media gateway TrGW4a to use the media resource information in the SDP response, and allocates the media resource for connecting to the near end, and the ALG4 determines the ALG4 according to the ALG related information on the received path.
  • the indication information may further include an association identifier for associating the subsequent SDP request;
  • Each ALG on the media path can determine whether there is an optimized media path. If it is determined that there is an optimized media path between the ALGx, the returned response carries the indication information to indicate that the optimized media path is established with the ALGx, and the other After receiving the response with the indication information, the ALG can no longer determine whether there is an optimized media path.
  • the ALG determines whether there is an optimized media path according to location-related information such as geographic location information or ALG domain name carried in the SDP request.
  • location-related information such as geographic location information or ALG domain name carried in the SDP request.
  • ALG1 carries the geographical location information of TrGWlb in the SDP request message
  • ALG4 determines TrGWlb and TrGW4b geography. If the location is close, it is considered that there is an optimized path, and an indication information for establishing an optimized media path with ALG1 is generated.
  • the indication information mainly carries information related to ALG1, and may also carry information related to ALG4.
  • the ALG-related information may be location-related information, such as geographic location information (including information of the ALG-controlled TrGW) or an ALG domain name, or may be the current media path of the associated ALG (in this embodiment, ALG1). That is, the serial number information of the original media path.
  • Step 208 The ALG4 generates an SDP response by using the media resource information of the TrGW 4a for connecting the near end, and adds the generated indication information to the SDP response, and sends the SDP response, for example, by forwarding the SIP signaling to carry the SDP response. ;
  • Step 209 The SDP response arrives at ALG3, and the ALG3 controls the media gateway TrGW3 to use the media resource information in the SDP response, and allocates a media resource for connecting to the near end, and the ALG3 uses the media resource information of the TrGW3 for connecting the near end to replace the SDP response. Media resource information, and then forward the SDP response, for example, by forwarding the SIP signaling to carry the SDP response for forwarding;
  • TrGW4a the media connection between TrGW4a and TrGW3 has been established.
  • Step 210 The SDP response arrives at ALG2, and the ALG2 controls the media gateway TrGW2 to use the media resource information in the SDP response, and allocates a media resource for connecting to the near end, and the ALG2 replaces the SDP response with the media resource information of the TrGW2 for connecting the near end. Media resource information, and then forward the SDP response, for example, by forwarding the SIP signaling to carry the SDP response for forwarding;
  • TrGW3 the media connection between TrGW3 and TrGW2 has been established.
  • Step 211 The SDP response arrives at ALG1, and the ALG1 determines that the SDP response carries indication information that is desired to establish an optimized path, and the indication information is related thereto, and then selects TrGWlb as a media gateway for optimizing the media path, and allocates media for connecting the near end.
  • the ALG1 generates an SDP response by using the TrGWlb to connect the near-end media resource information, and sends the SDP response, for example, by forwarding the SIP signaling to carry the SDP response, and the UE1 uses the media resource information in the received SDP response to negotiate.
  • the ALG may select according to the location information related to the ALG4 carried in the indication information, or may also select according to other methods in the prior art.
  • Step 212 At the same time as step 208, the ALG4 selects the TrGW 4b as a media gateway for optimizing the media path, and allocates a media resource for connecting to the near end.
  • the ALG4 generates an SDP request by using the TrGW 4b to connect the near-end media resource information, and sends the SDP request.
  • the SDP request for example, by sending an INVITE request, is sent by the message body of the SIP request to carry the SDP request, and the SIP request may carry the association identifier generated in step 207, which may be carried in the header, for example, by Target- The Dialog (target session) header field or the Replaces header field is carried, and can also be carried by the message body, that is, carried by the SDP request;
  • Step 213 The SDP request arrives at the ALG5, and the ALG5 selects the TrGW5 as the media gateway, controls the media gateway to use the media resource information in the SDP request, and allocates the media resource for connecting to the near end, and the ALG5 uses the TrGW5 to connect the near-end media resource.
  • the information generates an SDP request, and sends the SDP request, for example, by forwarding the SIP signaling to carry the SDP request for forwarding;
  • the media paths of ALG1 to ALG4 are established.
  • the ALG4 initiates the session to the ALG1 through the step 212-step 213.
  • the ADP4 sends the association identifier in the SDP response sent by the ALG4 in step 208, and the SDP request sent by the ALG4 in step 212 also carries the association identifier.
  • the SDP response and the SDP request it is considered that the established ALG1 to ALG4 session is associated with ALG4 to initiate a new session, which is the session under the same call.
  • Step 214 The SDP request finally arrives at ALG1.
  • the ALG1 controls the media gateway TrGWlb to use the media resource information in the SDP request, and allocates a media resource for connecting to the remote end.
  • the media resource is a resource of the optimized media path, and the ALG1 is used by the TrGWlb.
  • TrGWlb the media connection between TrGWlb and TrGW5 has been established.
  • Step 215 The SDP response arrives at the ALG5, and the ALG5 controls the media gateway TrGW5 to use the media resource information in the SDP response, and allocates a media resource for connecting to the remote end, and the ALG5 generates an SDP response by using the TrGW5 to connect the remote media resource information, and Sending the SDP response, for example, by forwarding the SIP signaling to carry the SDP response, and the SDP response arrives at the ALG4, and the ALG4 controls the TrGW4b to use the media resource information in the SDP response;
  • TrGW5 and TrGW4b are established, ALG1 to ALG4 The optimized media path is established.
  • Step 216 If the ALG1 wants to release the media gateways in the original media path, the ALG1 may send a new SDP request along the original session path, where the invalid media resource information is carried to indicate that the resources on the media path are released, for example, by sending a SIP message.
  • the relNVITE request is sent by the message body of the SIP request to carry the SDP request;
  • Step 217 The SDP request arrives at the ALG2, and the ALG2 releases the TrGW2 resource for the original media path, and forwards the SDP request, for example, by forwarding the SIP signaling to carry the SDP request for forwarding;
  • the resources of the original media path are forwarded, and the SDP request is forwarded, for example, by forwarding the SIP signaling to carry the SDP request.
  • Steps 216-218 are optional steps.
  • Step 219 After step 215, or after step 218, if TrGW4b is different from TrGW4a, ALG4 controls TrGW4b to allocate media resources for connecting to the remote end, and ALG4 uses TrGW4b to connect to the remote media resource information to generate SDP. Requesting, and transmitting the SDP request to UE2, for example, if the SDP request can be carried by forwarding SIP signaling after step 218, or if relNVITE (re-invitation) request is sent by sending SIP signaling after step 215 Transmitting, by the message body of the SIP request, the SDP request to send;
  • Step 220 The SDP request arrives at the UE2, and the UE2 uses the media resource information in the SDP request to perform media negotiation, and sends an SDP response to carry the media resource information of the UE2, for example, sends a "200 OK" response of the SIP signaling, and responds by using the SIP.
  • the message body carries the SDP response to send; thus, the media connection between UE2 and TrGW4b is established.
  • Step 221 After step 220, or after step 218, the ALG4 sends a new SDP response along the original session path, where the invalid media resource information is carried to indicate that the resource on the media path has been released, for example, if at step After 220, the SDP response may be forwarded by forwarding the SIP signaling, or if, after step 218, by sending a "200 OK" response of the SIP signaling, the message body that responds by the SIP carries the SDP response to send;
  • Step 222 The SDP response arrives at the ALG3, and the ALG3 forwards the SDP response, for example, by forwarding the SIP signaling to carry the SDP response.
  • Step 223 The SDP response reaches ALG2, and the ALG2 forwards the SDP response, for example, by forwarding.
  • SIP signaling carries the SDP response for forwarding;
  • the optimized media path is established.
  • the media path is UE1, TrGWlb, TrGW5, TrGW4b, UE2, and the original media paths TrGW1a, TrGW2, TrGW3, TrGW4a, UE2 are released through steps 216 ⁇ 223, where the media between TrGW4a and UE2
  • the connection is updated to a media connection between TrGW 4b and UE 2 via steps 219-220.
  • the media connection between TrGWla and UE1 is not established in the original media path establishment process, because it is unnecessary to establish the media connection by using the optimized media path.
  • FIG. 3 is a flowchart corresponding to the embodiment of FIG. 1A, and mainly includes the following steps: Steps 301-310, which are the same as steps 201-210 in FIG. 2;
  • Steps 311 to 312 are the same as steps 212 to 213 in FIG. 2;
  • step 313 the SDP response in step 310 reaches ALG1, and the ALG1 determines that the SDP response carries the indication information that the optimization path is desired to be established, and the indication information is related thereto, and then waits for the request to establish a new media path, and the new media path is established in step 312.
  • the SDP request arrives at ALG1, ALG1 selects TrGWlb as the media gateway for optimizing the media path, allocates media resources for connecting to the near end, and ALG1 generates an SDP response with TrGWlb for connecting the near-end media resource information, and sends the SDP response. For example, by forwarding the SDP response by forwarding the SIP signaling on the original session path;
  • step 310 Since the SDP response of step 310 and the SDP request of step 312 may arrive at ALG1 in sequence, if ALG1 first receives the SDP request of 312, the SDP response in step 310 may be directly executed. 313.
  • the selection of the TrGW by the ALG1 may be based on the location-related information in the indication information, or may be determined based on the direction or destination of the message in step 312.
  • Steps 314 ⁇ 323 are the same as steps 214 ⁇ 223 in FIG. 2;
  • Steps 316 ⁇ 323 are released, wherein the media connection between TrGW4a and UE2 is updated to a media connection between TrGW4b and UE2 through steps 319-320.
  • the media connection between the TrGW1a and the UE1 is not established in the original media path establishment process, because it is not necessary to establish the media connection by using the optimized media path.
  • FIG. 4 is a flowchart corresponding to the embodiment of FIG. 1A. The difference from the embodiment 1 is that, in this embodiment, the SDP request is sent by the ALG1, and the method mainly includes the following steps:
  • Steps 401-406 are the same as steps 201-206 in FIG. 2;
  • Step 407 The ALG4 determines, according to the information related to each ALG on the received path, that there is a shorter path between the ALG4 and the ALG1, and then generates indication information to be added to the SDP response, to indicate that the optimization between the ALG1 establishment and the ALG4 is desired.
  • the indication information may not carry the association identifier, but carries the relevant information of the ALG4, such as the address information of the ALG4.
  • Steps 408 to 411 are the same as steps 208 to 211 in FIG. 2;
  • Step 412 The ALG1 controls the TrGWlb to allocate a media resource for connecting to the remote end, and the ALG1 generates an SDP request by using the TrGWlb to connect the remote media resource information, and sends the SDP request, for example, an INVITE request through SIP signaling, through the SIP.
  • the requested message body carries the SDP request for sending, and the target of the request is obtained from the information related to ALG4 included in the indication information;
  • step 411 and step 412 are not limited.
  • Step 413 The SDP request arrives at the ALG5, and the ALG5 controls the media gateway TrGW5 to use the media resource information in the SDP request, and allocates a media resource for connecting to the remote end, and the ALG5 generates an SDP request by using the TrGW5 to connect the remote media resource information, and Sending the SDP request, for example, by forwarding the SIP signaling to carry the SDP response for forwarding;
  • Step 414 the SDP request arrives at the ALG4, and the ALG4 controls the TrGW4b to use the media resource information in the SDP request, and allocates a media resource for connecting to the near end, and the ALG4 generates an SDP response by using the TrGW4b to connect the near-end media resource information, and sends the SDP response.
  • the SDP response for example, by sending a "200 OK" response of the SIP signaling, and transmitting the SDP response by the message body of the response; At this point, the media connection between TrGW4b and TrGW5 is established.
  • Step 415 The SDP response arrives at the ALG5, and the ALG5 controls the TrGW5 to use the media resource information in the SDP response, and allocates a media resource for connecting to the near end, and the ALG5 generates an SDP response by using the TrGW5 to connect the near-end media resource information, and sends the SDP response.
  • the SDP response for example, by forwarding the SIP signaling to carry the SDP response, the SDP response arrives at ALG1, and the ALG1 controls the TrGWlb to use the media resource information in the SDP response;
  • TrGW5 the media connection between TrGW5 and TrGWlb is established.
  • Steps 416 ⁇ 418 are the same as steps 216 ⁇ 218 in FIG. 2;
  • Step 419 after step 413, or after step 418, if TrGW4b is different from TrGW4a, ALG4 controls TrGW4b to allocate media resources for connecting to the remote end, and ALG4 uses TrGW4b to connect to the remote media resource information to generate SDP.
  • Requesting, and transmitting the SDP request for example, if, after step 418, the SDP request can be carried by forwarding SIP signaling, or if after step 413, by sending a relNVITE request for SIP signaling, The message body of the SIP request carries the SDP request to send;
  • Step 420 The SDP request arrives at the UE2, and the UE2 uses the media resource in the SDP request, and sends an SDP response to carry the media resource information of the UE2, for example, a "200 OK" response for sending the SIP signaling, and the message body carried by the SIP response carries The SDP response is sent;
  • Step 421 Optionally, after step 418, or after step 420, the ALG4 sends a new SDP response along the original session path, where the invalid media resource information is carried to indicate that the resource on the media path has been released, for example, If after step 420, the SDP response may be carried by forwarding the SIP signaling, or if after step 418, by sending a "200 OK" response of the SIP signaling, the message body responding by the SIP carries the SDP response. Send
  • Step 422 The SDP response arrives at the ALG3, and the ALG3 forwards the SDP response, for example, by forwarding the SIP signaling to carry the SDP response for forwarding;
  • Step 423 The SDP response reaches ALG2, and the ALG2 forwards the SDP response, for example, by forwarding.
  • SIP signaling carries the SDP response for forwarding
  • Steps 416 ⁇ 423 are released, wherein the media connection between TrGW4a and UE2 is updated to a media connection between TrGW4b and UE2 through steps 419-420.
  • the media connection between the TrGW1a and the UE1 is not established in the original media path establishment process, because it is not necessary to establish the media connection by using the optimized media path.
  • the call setup time can be effectively shortened, and the user is provided with a better use experience.

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Description

一种优化媒体路径的建立方法和实现该方法的信令网关 技术领域
本发明涉及移动通信技术领域， 尤其涉及一种优化 IMS媒体路径的建立 方法和实现该方法的信令网关。
背景技术
IP多媒体子系统（ IP Multimedia Core Network Subsystem, 简称为 IMS ) 是由第三代合作伙伴计划（ 3rd Generation Partnership Project, 简称 3GPP )提 出的一种基于 IP的网络架构， 该系统构建了一种开放而灵活的业务环境， 支 持多媒体应用， 能够为用户提供丰富的多媒体业务。
IMS可以分为控制层和业务层， 其中， 控制层主要包括用于业务触发和 控制的会话控制功能（Call Session Control Function,简称为 CSCF ) ,而 CSCF 又可以分为代理 CSCF( Proxy CSCF,简称为 P-CSCF )、查询 CSCF( Interrogating CSCF, 简称为 I-CSCF )和月良务 CSCF ( Serving CSCF, 简称为 S-CSCF ) , 其中， I-CSCF 和 S-CSCF 为可选。 而业务层主要包括一系列的应用服务器 ( Application Server, 简称为 AS ) , 用于提供具体的服务业务， AS可以是独 立的实体， 也可以存在于 S-CSCF中。 其运行方式为： 控制层（S-CSCF )根 据用户的签约信息控制业务触发， 调用 AS上的业务， 实现业务功能。
同时， IMS网络中还存在各种各样的处理 IMS信令和媒体的网关设备， 比如 P-CSCF及其控制的访问控制网关 （Access Gateway, 简称为 AGW ) , 交互边界控制功能（ Interworking Border Control Function, 简称为 I-BCF )及 其控制的交互边界网关 （Interworking Border Gateway, 简称为 I-BGW ) , 信 令和媒体网关合一的会话边界控制 （Session Border Control, 简称为 SBC ) , 应用层网关（Application Layer Gateway, 简称为 ALG )及其控制的传输网关 ( Transmit Gateway, 简称 TrGW )等， 这些网关的作用主要是对媒体路径进 行分段， 从而实现不同网络间的互通， 比如公网设备和私网设备间的互通， 还有通过编码转换实现具有不同编码功能的实体间的互通，为了描述的方便， 可以将所有信令网关称为 ALG, 其所控制的媒体网关称为 TrGW, 也可以将 处理 IMS信令和媒体的网关设备统称为信令媒体网关，比如，可以将 P-CSCF 和 AGW视为一个信令媒体网关。 为方便描述， 将通话建立请求或通话更新 请求的来向称为媒体网关的近端， 去向称为媒体网关的远端。
由于会话的最终目的是要实现媒体连接， 因此需要在会话中协商媒体资 源信息， IMS 系统中协商媒体资源信息的协议是会话描述协议 （ Session Description Protocol, 简称为 SDP ) , 协议的交互的方式为请求回应模式， 即 一个 SDP请求必须有一个 SDP回应（除非发生错误而拒绝）， SDP请求和回 应的内容都是媒体资源信息， 媒体资源信息包括媒体所有者信息 （包括地址 信息） , 媒体连接地址， 媒体类型以及与媒体类型相关的媒体端口和编解码 器信息等， SDP回应的内容中， 媒体数量、 类型和顺序必须与 SDP请求中的 媒体数量， 类型和顺序完全相同。 SDP 协议的内容通过会话初始化协议 ( Session Initiation Protocol, SIP ) 消息的消息体携带， 交互过程独立于 SIP 的请求回应模式， 也就是说 SIP的请求或回应消息中可以携带 SDP请求， 也 可以携带 SDP回应， 也可以不携带 SDP协议内容。
以下为了描述的方便， 图中只列出了 ALG和 TrGW实体， 其他 IMS实 体仅路由 SIP信令消息， 不影响该文的描述。
图 1A为现有的建立优化 IMS媒体路径示意图， 描述了 IMS终端 UE-A 与 IMS终端 UE-B之间的不同媒体路径以及相应的信令路径。
如图 1A所示， 现有的呼叫过程建立的媒体路径为： UE1、 TrGWla、 TrGW2、 TrGW3、 TrGW4a、 UE2, 而优化后的媒体路径为： UE1、 TrGWlb、 TrGW5、 TrGW4b、 UE2, 优化后的媒体路径比未优化的媒体路径短了， 少了 一个 TrGW,因而优化的媒体路径更节省资源，也更高效。其中信令网关 ALG1 控制着 TrGWla和 TrGWlb, ALG2控制着 TrGW2, ALG3控制着 TrGW3 , ALG4控制着 TrGW4a和 TrGW4b , ALG5控制着 TrGW5。
图 1B为现有的建立优化 IMS媒体路径的流程图，与图 1A的示意图相对 应， 主要包括以下步骤：
步骤 101、 UE1向 UE2发送 SDP请求以协商媒体资源信息， 比如通过发 送 SIP的呼叫信令， 即 INVITE (邀请 )请求， 或更新信令， 即 relNVITE (重 邀请）请求， 以该 SIP请求的消息体携带该 SDP请求， SDP请求的内容为 UE1的媒体资源信息；
步骤 102、 SDP请求到达信令网关 ALG1 , 信令网关 ALG1选择 TrGWla 作为媒体网关， 控制该媒体网关使用 SDP请求中的媒体资源信息， 并分配用 于连接远端的媒体资源， ALG1用 TrGWla的用于连接远端的媒体资源信息 代替 SDP请求中的媒体资源信息， 然后将 ALG1的相关信息及与会话标识相 关的信息加入该 SDP请求后转发 SDP请求， 比如通过转发 SIP信令携带该 SDP请求来转发；
步骤 103、 SDP请求到达信令网关 ALG2, ALG2选择 TrGW2作为媒体 网关， 控制该媒体网关使用 SDP请求中的媒体资源信息， 并分配用于连接远 端的媒体资源， ALG2用 TrGW2 的用于连接远端的媒体资源信息代替 SDP 请求中的媒体资源信息， 然后将 ALG2的相关信息及与会话标识相关的信息 加入该 SDP请求后转发 SDP请求， 比如通过转发 SIP信令携带该 SDP请求 来转发；
步骤 104、 SDP请求到达信令网关 ALG3 , ALG3选择 TrGW3作为媒体 网关， 控制该媒体网关使用 SDP请求中的媒体资源信息， 并分配用于连接远 端的媒体资源， ALG3用 TrGW3 的用于连接远端的媒体资源信息代替 SDP 请求中的媒体资源信息， 然后将 ALG3的相关信息及与会话标识相关的加入 该 SDP请求后转发 SDP请求， 比如通过转发 SIP信令携带该 SDP请求来转 发；
步骤 105、 SDP请求到达信令网关 ALG4, ALG4选择 TrGW4a作为媒体 网关， 控制该媒体网关使用 SDP请求中的媒体资源信息， 并分配用于连接远 端的媒体资源， ALG4用 TrGW4a的用于连接远端的媒体资源信息代替 SDP 请求中的媒体资源信息， 然后将 ALG4的相关信息及与会话标识相关的加入 该 SDP请求后转发 SDP请求， 比如通过转发 SIP信令携带该 SDP请求来转 发， 转发的 SDP请求最终到达 UE2;
步骤 106、UE2使用 SDP请求中的媒体资源信息进行协商，然后发送 SDP 响应， 携带 UE2的媒体资源信息， 比如通过 SIP信令的 "200 OK" 回应， 以 该 SIP回应的消息体携带该 SDP响应 , 该 SDP响应到达 ALG4;
步骤 107、 ALG4根据收到的路径上的各 ALG相关的信息， 判断 ALG4 与 ALG1间存在一个更短路径， 于是向 ALG1发送 SIP的协商请求消息以建 立第二媒体路径段，并携带一些收到的 ALG1相关的信息，比如发送不带 SDP 请求的 INVITE消息， 消息的目标为 ALG1的地址， 并携带 ALG1提供的会 话标识相关信息， 该 SIP信令将创建一个新的会话信令通道；
步骤 108、 SIP 的协商请求消息被路由到 ALG5, ALG5 转发该消息至
ALG1 ;
步骤 109、 SIP的协商请求消息到达 ALG1 , ALG1选择 TrGWlb作为媒 体网关 （可根据协商请求消息的来向等信息进行选择） ， 分配用于连接远端 的媒体资源， 并关联两次媒体协商， ALG1以 TrGWlb用于连接远端的媒体 资源信息生成 SDP请求，并发送该 SDP请求以协商媒体资源信息， 比如通过 发送 SIP信令的 "200 OK" 回应， 以该 SIP回应的消息体携带该 SDP请求； 步骤 110、 SDP请求到达信令网关 ALG5 , ALG5选择 TrGW5作为媒体 网关， 控制该媒体网关使用 SDP请求中的媒体资源信息， 并分配用于连接远 端的媒体资源， ALG5用 TrGW5 的用于连接远端的媒体资源信息代替 SDP 请求中的媒体资源信息， 然后转发 SDP请求， 比如通过转发 SIP信令携带该 SDP请求来转发， 转发的 SDP请求最终到达 ALG4;
步骤 111、 ALG4决定选择第二媒体路径段， 于是选择 TrGW4b作为媒体 网关， 控制该媒体网关使用 SDP请求中的媒体资源信息， 并分配用于连接远 端的媒体资源， ALG4用 TrGW4b的用于连接远端的媒体资源信息代替 SDP 请求中的媒体资源信息， 然后转发 SDP请求， 比如通过 SIP信令的 UPDATE (更新 )请求的消息体携带该 SDP请求来转发， 转发的 SDP请求最终到达 UE2;
步骤 112、 UE2收到新的 SDP请求， 更新为使用 SDP请求中的媒体资源 信息， 并发送 SDP响应至 ALG4, SDP响应内容为 UE2的媒体资源信息， 比 如通过 SIP信令的 "200 OK"回应， 以该 SIP回应的消息体携带该 SDP响应 , 该 SDP响应到达 ALG4;
步骤 113、 ALG4用 TrGW4b的媒体资源信息生成 SDP响应， 并发送该 SDP响应至 ALG5, 比如通过发送 SIP信令的 ACK (确认）请求， 以该 SIP 请求的消息体携带该 SDP回应； 步骤 114、 SDP响应到达信令网关 ALG5, ALG5用 TrGW5的媒体资源 信息代替 SDP响应中的媒体资源信息， 然后转发 SDP响应至 ALG1 , 比如通 过转发 SIP信令携带该 SDP响应来转发， 转发的 SDP响应最终到达 ALG1 , ALG1控制 TrGWlb使用 SDP响应中的媒体资源信息；
步骤 115、 与步骤 113同时， ALG4生成 SDP响应携带无效媒体资源信 息以指示释放原会话信令通道上分配的媒体网关， 比如将媒体的端口号设置 为 0,并通过原会话信令通道发送该 SDP响应，比如通过发送 SIP信令的 "200 OK" 回应， 以该 SIP回应的消息体携带该 SDP回应；
步骤 116~117、 SDP响应分别经过 ALG3和 ALG2到达 ALGl , ALG3、 ALG2及 ALG1释放原会话信令通道上分配的各媒体网关，即 TrGW3、 TrGW2 及 TrGWla;
步骤 118、 ALGl控制 TrGWlb分配媒体资源信息， 并以此媒体资源信息 替换步骤 117中的 SDP响应中的媒体资源信息， 然后转发 SDP响应， 比如通 过转发 SIP信令携带该 SDP响应来转发， 转发的 SDP响应最终到达 UE1。
至此，优化的媒体路径便建立起来，媒体路径为 UE1、 TrGWlb、 TrGW5、
TrGW4b、 UE2。
由上述的描述可知， 现有的优化媒体路径建立方法耽误了原会话信令通 道上的 SDP请求与响应的完成时间， 从而会影响呼叫建立时间。 发明内容
本发明要解决的技术问题是提供一种优化媒体路径的建立方法和实现该 方法的信令网关， 有效缩短呼叫建立时间。
为解决上述技术问题， 本发明提供了一种优化媒体路径的建立方法， 用 于 IMS网络中， 所述方法包括：
转发 SDP请求与响应的过程中，在接收到第一会话的 SDP响应时，第一
ALG判断与第二 ALG间存在优化的媒体路径， 则在发送第一会话的 SDP响 应时， 并在发送的 SDP响应中携带指示信息；
所述第一 ALG发送以所述第二 ALG为目标的 SDP请求； 以及 所述第二 ALG收到携带所述指示信息的第一会话的 SDP响应后， 或者 在收到以所述第二 ALG为目标的 SDP请求和携带所述指示信息的第一会话 的 SDP响应后， 发送第一会话的 SDP响应。
所述指示信息用来指示与所述第二 ALG间建立优化媒体路径，所述第一 ALG和第二 ALG发送的第一会话的 SDP响应中还携带用于建立优化媒体路 径的资源信息。
所述第一会话的 SDP响应中的指示信息中携带有关联标识， 在所述第一 ALG发送以所述第二 ALG为目标的 SDP请求的步骤中，在携带所述 SDP请 求的 SIP消息中携带所述关联标识。
该方法还包括： 所述第二 ALG收到以所述第二 ALG为目标的 SDP请求 后， 发起第一会话媒体路径资源的释放。
所述指示信息中包含与第二 ALG相关的信息。
本发明还提供了另一种优化媒体路径的建立方法， 用于 IMS网络中， 所 述方法包括：
转发 SDP请求与响应的过程中，在接收到第一会话的 SDP响应时，第一
ALG判断与第二 ALG间存在优化的媒体路径， 则在发送第一会话的 SDP响 应时， 在所述发送的 SDP响应中携带指示信息； 以及
所述第二 ALG收到携带所述指示信息的第一会话的 SDP响应后， 以所 述第一 ALG为目标发送 SDP请求。
如权利要求 6所述的方法，其中，所述指示信息用来指示与所述第二 ALG 间建立优化媒体路径， 该方法还包括：
所述第二 ALG收到携带所述指示信息的第一会话的 SDP响应后， 发送 第一会话的 SDP响应，所述发送的 SDP响应携带用于建立优化媒体路径的资 源信息。
该方法还包括： 所述第一 ALG收到以本 ALG为目标的 SDP请求后， 发 送第二会话的 SDP响应； 所述第二 ALG收到第二会话的 SDP响应后， 发起 第一会话媒体路径资源的释放。
所述指示信息中包含与所述第一 ALG相关的信息和所述第二 ALG相关 的信息。
本发明还提供一种建立优化媒体路径的 ALG, 其包括： 切出模块和切入 模块， 其中：
所述切出模块设置为： 在转发 SDP请求与响应的过程中， 在接收到第一 会话的 SDP响应时， 判断本 ALG与第一会话媒体路径上的另一 ALG间存在 优化的媒体路径，则在发送第一会话的 SDP响应时，在发送的 SDP响应中携 带指示信息； 以及发送以所述另一 ALG为目标的 SDP请求；
所述切入模块设置为：在收到携带与本 ALG相关的指示信息的第一会话 的 SDP响应后，或者在收到以本 ALG为目标的 SDP请求和携带与本 ALG相 关的指示信息的第一会话的 SDP响应后， 发送第一会话的 SDP响应。
所述切出模块转发的第一会话的 SDP响应和所述 SDP请求中都携带关联 标识。
所述切出模块和切入模块发送的第一会话的 SDP响应还携带用于建立优 化媒体路径的资源信息。
该 ALG还包括中间模块， 其设置为： 接收到携带与本 ALG无关的第一 会话的 SDP响应后， 发送携带所述与本 ALG无关的指示信息的第一会话的 SDP响应。
本发明还提供另一种建立优化媒体路径的 ALG, 其包括： 切出模块和切 入模块， 其中： 所述切出模块设置为： 在转发 SDP请求与响应的过程中， 在接收到第一 会话的 SDP响应时， 判断与第一会话媒体路径上的另一 ALG间存在优化的 媒体路径，则在发送第一会话的 SDP响应时，在发送的 SDP响应中携带指示 信息；
所述切入模块设置为：在收到携带与本 ALG相关的指示信息的第一会话 的 SDP响应后，以指示信息中指示的与本 ALG间存在优化的媒体路径的 ALG 为目标发送 SDP请求。
所述切入模块还设置为：在收到携带与本 ALG相关的指示信息的第一会 话的 SDP响应后， 发送第一会话的 SDP响应， 发送的 SDP响应； 所述切出模块和切入模块发送的第一会话的 SDP响应还携带用于建立优 化媒体路径的资源信息。
所述切出模块还设置为： 收到以本 ALG为目标的 SDP请求后， 发送第 二会话的 SDP响应；
所述切入模块还设置为： 在接收到第二会话的 SDP响应后， 发起第一会 话媒体路径资源的释放。
该 ALG还包括中间模块， 其设置为： 接收到携带与本 ALG无关的指示 信息的第一会话的 SDP响应后， 发送携带所述与本 ALG无关的指示信息的 第一会话的 SDP响应。
釆用本发明所述方法和信令网关， 能够有效缩短呼叫建立时间， 为用户 提供更好的使用体验。 附图概述
附图用来提供对本发明的进一步理解， 并且构成说明书的一部分， 与本 发明的实施例一起用于解释本发明， 并不构成对本发明的限制。 在附图中： 图 1A为现有的建立优化 IMS媒体路径示意图；
图 1B为现有的建立优化 IMS媒体路径的流程图；
图 2为实施例一的流程图；
图 3为实施例二的流程图；
图 4为实施例三的流程图。
本发明的较佳实施方式
本发明的发明构思是， 通过主动发起呼叫来缩短建立时间。
本发明的方法包括：
a )转发会话描述协议（SDP )请求与响应的过程中， 在接收到第一会话 的 SDP响应时， 第一信令网关 （ALG )判断与第二 ALG间存在优化的媒体 路径，则在发送第一会话的 SDP响应时，在发送的 SDP响应中携带指示信息； b )所述第一 ALG发送以所述第二 ALG为目标的 SDP请求；
c )所述第二 ALG收到携带所述指示信息的第一会话的 SDP响应后， 或 者在收到以所述第二 ALG为目标的 SDP请求和携带所述指示信息的第一会 话的 SDP响应后， 发送第一会话的 SDP响应。
所述发送的第一会话的 SDP响应中携带用于优化媒体路径的资源信息。 发送第一会话的 SDP响应用以完成第一会话的建立或第一会话的更新；
所述第二 ALG收到以所述第二 ALG为目标的 SDP请求后， 发起第一会 话媒体路径资源的释放。
所述第二 ALG在收到以自己为目标的上述 SDP请求后， 以第二会话发 送 SDP响应， 完成第二会话的建立。
所述第一会话的 SDP响应中的指示信息中携带有关联标识， 且所述第一 ALG发送以所述第二 ALG为目标的 SDP请求时，在携带所述 SDP请求的会 话初始协议（SIP ) 消息中携带所述关联标识； 所述第二 ALG根据所述关联 标识关联所述第一会话和第二会话。
在本方法中， 指示信息用于指示要建立的优化媒体路径与第二 ALG有 关， 主要包含与第二 ALG相关的信息， 例如第二 ALG控制的媒体网关的位 置， 或者包含第一会话的媒体路径中的序号信息。
或者在执行完步骤 a )后， 执行以下步骤：
bl )所述第二 ALG收到携带所述指示信息的第一会话的 SDP响应后， 向所述第一 ALG发送 SDP请求。
进一步地， 所述第二 ALG收到携带所述指示信息的第一会话的 SDP响 应后， 转发第一会话的 SDP响应， 以完成第一会话的建立或更新； 所述 SDP 响应携带用于优化媒体路径的资源信息。
进一步地， 所述第一 ALG收到以自己为目标的上述 SDP请求后， 发送 第二会话的 SDP响应， 以完成第二会话的建立。 所述第二 ALG收到第二会 话的 SDP响应后， 发起第一会话媒体路径资源的释放。 在本方法中， 指示信息用于指示在第一 ALG和第二 ALG之间建立优化 的媒体路径， 主要包含与第一 ALG相关的信息以及第二 ALG相关的信息。 所述与 ALG相关的信息例如可以是 ALG控制的媒体网关的位置信息。
对于一个信令网关而言， 其既可以是上述第一信令网关也可以是上述第 二信令网关。 在不同的通话流程中， 一个信令网关可能同时作为第一信令网 关和第二信令网关， 因此， 其应具有上述第一信令网关所有的功能也应具有 上述第二信令网关所有的功能。
一种实现上述方法的信令网关包括： 切出模块和切入模块， 其中： 所述切出模块， 用于在转发会话描述协议（ SDP )请求与响应的过程中， 在接收到第一会话的 SDP响应时， 判断与第一会话媒体路径上的某 ALGx间 如果存在优化的媒体路径， 则在转发第一会话的 SDP响应时， 在所述 SDP 响应中携带指示信息； 以及用于发送以 ALGx为目标的 SDP请求；
所述切入模块，用于在收到携带与本 ALG有关的指示信息的第一会话的 SDP响应后， 或者在收到以本 ALG为目标的 SDP请求和携带与本 ALG有关 的指示信息的第一会话的 SDP响应后， 转发第一会话的 SDP响应。
该信令网关还可以是第一信令网关和第二信令网关之间路径上的其他信 令网关， 此时， 该信令网关还可包括中间模块， 用于接收到携带与本 ALG无 关的第一会话的 SDP响应后， 发送携带所述与本 ALG无关的指示信息的第 一会话的 SDP响应。
另一种实现上述方法的信令网关包括： 切出模块和切入模块， 其中： 所述切出模块， 用于在转发会话描述协议（SDP )请求与响应的过程中， 在接收到第一会话的 SDP响应时， 判断与第一会话媒体路径上的某 ALGx间 存在优化的媒体路径，则在转发第一会话的 SDP响应时，在所述 SDP响应中 携带指示信息；
所述切入模块，用于在收到携带所述指示信息的第一会话的 SDP响应后 , 向指示信息中指示的 ALGx发送 SDP请求。 该信令网关还可以是第一信令网关和第二信令网关之间路径上的其他信 令网关， 此时， 该信令网关还可包括中间模块， 用于接收到携带与本 ALG无 关的第一会话的 SDP响应后， 发送携带所述与本 ALG无关的指示信息的第 一会话的 SDP响应。
以下结合附图对本发明的优选实施例进行说明， 应当理解， 此处所描述 的优选实施例仅用于说明和解释本发明， 并不用于限定本发明。
以下实施例的图中， 虚线表示的是可选或有条件的信令消息。
实施例一
图 2所示为相应于图 1A的本实施例的流程图， UE1与 UE2建立通话， 其中包括多次会话建立过程， 主要包括以下步骤：
步骤 201~206、 与图 1B中的步骤 101~106相同;
步骤 207、 ALG4收到 SDP响应， ALG4控制媒体网关 TrGW4a使用 SDP 响应中的媒体资源信息， 并分配用于连接近端的媒体资源， ALG4根据收到 的路径上的各 ALG相关的信息，判断 ALG4与 ALG1间是否存在优化的媒体 路径， 例如 ALG4根据地理位置信息判断与 ALG1间地理位置比较近， 存在 更短路径， 于是生成要添加到 SDP 响应中的指示信息， 以指示希望建立与 ALG1 间的优化媒体路径， 该指示信息还可包含关联标识， 用以关联后续的 SDP请求；
至此， UE2与 TrGW4a间的媒体连接建立起来了。
媒体路径上的各个 ALG均可判断是否存在优化的媒体路径，如果判断与 某 ALGx之间存在优化的媒体路径， 则在返回的响应中携带指示信息， 以指 示与该 ALGx建立优化媒体路径， 其他 ALG收到携带指示信息的响应后， 可 不再判断是否存在优化媒体路径。
ALG根据 SDP请求中携带的地理位置信息或 ALG域名等与位置相关的 信息来判断是否存在优化的媒体路径， 例如 ALG1在 SDP请求消息中携带了 TrGWlb的地理位置信息，则 ALG4判断 TrGWlb与 TrGW4b地理位置艮近， 则认为存在优化路径， 生成与 ALG1建立优化媒体路径的指示信息。 指示信息中主要携带有与 ALG1相关的信息， 还可以携带有与 ALG4相 关的信息。 所述与 ALG相关的信息可以是与位置相关的信息， 例如地理位置 信息（包括该 ALG控制的 TrGW的信息 )或 ALG域名， 也可以是相关 ALG (本实施例中为 ALG1 )所在当前媒体路径即原媒体路径的序号信息。
步骤 208、 ALG4用 TrGW4a的用于连接近端的媒体资源信息生成 SDP 响应， 并在该 SDP响应中添加生成的指示信息， 并发送该 SDP响应， 比如通 过转发 SIP信令携带该 SDP响应来转发；
步骤 209、 SDP响应到达 ALG3 , ALG3控制媒体网关 TrGW3使用 SDP 响应中的媒体资源信息， 并分配用于连接近端的媒体资源， ALG3用 TrGW3 的用于连接近端的媒体资源信息代替 SDP响应中的媒体资源信息， 然后转发 SDP响应， 比如通过转发 SIP信令携带该 SDP响应来转发；
至此， TrGW4a与 TrGW3间的媒体连接建立起来了。
步骤 210、 SDP响应到达 ALG2, ALG2控制媒体网关 TrGW2使用 SDP 响应中的媒体资源信息， 并分配用于连接近端的媒体资源， ALG2用 TrGW2 的用于连接近端的媒体资源信息代替 SDP响应中的媒体资源信息， 然后转发 SDP响应， 比如通过转发 SIP信令携带该 SDP响应来转发；
至此， TrGW3与 TrGW2间的媒体连接建立起来了。
步骤 211、 SDP响应到达 ALG1 , ALG1判断 SDP响应中携带希望建立优 化路径的指示信息， 且指示信息与其相关， 于是选择 TrGWlb作为用于优化 媒体路径上的媒体网关， 分配用于连接近端的媒体资源， ALG1 以 TrGWlb 用于连接近端的媒体资源信息生成 SDP响应，并发送该 SDP响应， 比如通过 转发 SIP信令携带该 SDP响应来转发， UE1使用收到的 SDP响应中的媒体资 源信息协商媒体；
在本实施例中， 如果 ALG1管理多个 TrGW, 则 ALG可以根据指示信息 中携带的与 ALG4相关的位置信息来选择， 或者也可根据现有技术中的其他 方法进行选择。
至此， TrGW2与 TrGWla间的媒体连接和 UE1与 TrGWlb间的媒体连 接都建立起来了。 步骤 212、与步骤 208同时， ALG4选择 TrGW4b作为用于优化媒体路径 上的媒体网关， 分配用于连接近端的媒体资源， ALG4以 TrGW4b用于连接 近端的媒体资源信息生成 SDP请求， 并发送该 SDP请求， 比如通过发送 INVITE (邀请 )请求， 通过该 SIP请求的消息体携带该 SDP请求来发送， 该 SIP请求可携带步骤 207 中生成的关联标识， 可以在报头中携带， 比如通过 Target-Dialog (目标会话）头域或 Replaces (替换）头域携带， 也可以用消息 体携带， 即通过 SDP请求来携带；
步骤 213、 SDP请求到达 ALG5, ALG5选择 TrGW5作为媒体网关， 控 制该媒体网关使用 SDP请求中的媒体资源信息， 并分配用于连接近端的媒体 资源， ALG5以 TrGW5用于连接近端的媒体资源信息生成 SDP请求，并发送 该 SDP请求， 比如通过转发 SIP信令携带该 SDP请求来转发；
通过步骤 202-步骤 210, ALG1至 ALG4的媒体路径建立起来了。通过步 骤 212-步骤 213 , ALG4发起至 ALG1的会话， 由于步骤 208中 ALG4发送的 SDP响应中携带了关联标识， 且步骤 212中 ALG4发送的 SDP请求中也携带 关联标识， 因此当 ALG1收到该 SDP响应以及 SDP请求后，认为已经建立起 来的 ALG1至 ALG4的会话与 ALG4发起新会话是关联的， 均是同一个通话 下的会话。
步骤 214、 SDP请求最终到达 ALG1 , ALG1控制媒体网关 TrGWlb使用 SDP请求中的媒体资源信息， 并分配用于连接远端的媒体资源， 该媒体资源 为优化的媒体路径的资源， ALG1以 TrGWlb用于连接远端的媒体资源信息 生成 SDP响应， 并发送该 SDP响应， 比如通过发送 SIP信令的 "200 OK" 回应， 通过该 SIP回应的消息体携带该 SDP响应来发送；
至此， TrGWlb与 TrGW5间的媒体连接建立起来了。
步骤 215、 SDP响应到达 ALG5, ALG5控制媒体网关 TrGW5使用 SDP 响应中的媒体资源信息， 并分配用于连接远端的媒体资源， ALG5以 TrGW5 用于连接远端的媒体资源信息生成 SDP响应，并发送该 SDP响应， 比如通过 转发 SIP信令携带该 SDP响应来转发， SDP响应到达 ALG4, ALG4控制 TrGW4b使用该 SDP响应中的媒体资源信息；
至此， TrGW5与 TrGW4b间的媒体连接建立起来了， ALG1至 ALG4的 优化的媒体路径建立完成。
步骤 216、如果 ALG1希望释放原媒体路径中的各媒体网关， ALG1可沿 原会话路径发送新的 SDP请求， 其中携带无效的媒体资源信息以指示释放该 媒体路径上的资源， 比如通过发送 SIP信令的 relNVITE (重邀请 )请求， 通 过该 SIP请求的消息体携带该 SDP请求来发送；
步骤 217、 SDP请求到达 ALG2, ALG2释放 TrGW2用于原媒体路径的 资源， 并转发该 SDP请求， 比如通过转发 SIP信令携带该 SDP请求来转发； 步骤 218、 SDP请求到达 ALG3 , ALG3释放 TrGW3用于原媒体路径的 资源， 并转发该 SDP请求， 比如通过转发 SIP信令携带该 SDP请求来转发； 步骤 216-218为可选步骤。
步骤 219、 可以在步骤 215之后， 也可在步骤 218之后， 如果 TrGW4b 与 TrGW4a不同，则 ALG4控制 TrGW4b分配用于连接远端的媒体资源， ALG4 以 TrGW4b用于连接远端的媒体资源信息生成 SDP请求， 并发送该 SDP请 求至 UE2, 比如， 如果在步骤 218之后， 可通过转发 SIP信令携带该 SDP请 求来转发， 或如果在步骤 215之后， 通过发送 SIP信令的 relNVITE (重邀请 ) 请求， 通过该 SIP请求的消息体携带该 SDP请求来发送；
步骤 220、 SDP请求到达 UE2, UE2使用该 SDP请求中的媒体资源信息 进行媒体协商， 并发送 SDP响应以携带 UE2的媒体资源信息， 比如发送 SIP 信令的 "200 OK" 回应， 通过该 SIP回应的消息体携带该 SDP响应来发送； 至此， UE2与 TrGW4b间的媒体连接建立起来了。
步骤 221、 可在步骤 220之后， 也可在步骤 218之后， ALG4沿原会话路 径发送新的 SDP响应， 其中携带无效的媒体资源信息以指示该媒体路径上的 资源已经释放， 比如，如果在步骤 220之后，可通过转发 SIP信令携带该 SDP 响应来转发， 或如果在步骤 218之后， 通过发送 SIP信令的 "200 OK" 回应， 通过该 SIP回应的消息体携带该 SDP响应来发送；
步骤 222、 SDP响应到达 ALG3 , ALG3转发该 SDP响应， 比如通过转发 SIP信令携带该 SDP响应来转发；
步骤 223、 SDP响应到达 ALG2, ALG2转发该 SDP响应， 比如通过转发 SIP信令携带该 SDP响应来转发；
当执行了步骤 216-218后， 需执行步骤 221-223。
至此，优化的媒体路径便建立起来，媒体路径为 UE1、 TrGWlb、 TrGW5、 TrGW4b、 UE2, 原媒体路径 TrGWla、 TrGW2、 TrGW3、 TrGW4a、 UE2通 过步骤 216~223 被释放， 其中 TrGW4a与 UE2 间的媒体连接是通过步骤 219-220被更新为 TrGW4b与 UE2间的媒体连接。 本实施例原媒体路径建立 过程中没有建立 TrGWla和 UE1间的媒体连接，因为要使用优化的媒体路径， 就没必要再建立这段媒体连接了。
实施例二
图 3所示为相应于图 1A的本实施例的流程图， 主要包括以下步骤： 步骤 301~310、 与图 2中的步骤 201~210相同;
步骤 311~312、 与图 2中的步骤 212~213相同；
步骤 313、 步骤 310中的 SDP响应到达 ALG1 , ALG1判断 SDP响应中 携带希望建立优化路径的指示信息， 且指示信息与其相关， 于是等待建立新 媒体路径的请求，步骤 312的建立新媒体路径的新 SDP请求到达 ALG1 , ALG1 选择 TrGWlb作为用于优化媒体路径上的媒体网关， 分配用于连接近端的媒 体资源， ALG1以 TrGWlb用于连接近端的媒体资源信息生成 SDP响应， 并 发送该 SDP响应，比如通过转发原会话路径上的 SIP信令携带该 SDP响应来 转发；
由于在实现时， 步骤 310的 SDP响应和步骤 312的 SDP请求到达 ALG1 的先后顺序可能有所不同， 如果 ALG1先收到 312的 SDP请求， 则可以不等 待步骤 310中的 SDP响应， 直接执行步骤 313。
ALG1对 TrGW的选择除了根据指示信息中与位置相关的信息外， 还可 才艮据步骤 312消息的来向或去向决定。
步骤 314~323、 与图 2中的步骤 214~223相同；
至此，优化的媒体路径便建立起来，媒体路径为 UE1、 TrGWlb、 TrGW5、 TrGW4b、 UE2, 原媒体路径 TrGWla、 TrGW2、 TrGW3、 TrGW4a、 UE2通 过步骤 316~323 被释放， 其中 TrGW4a与 UE2 间的媒体连接是通过步骤 319-320被更新为 TrGW4b与 UE2间的媒体连接。 本实施例原媒体路径建立 过程中没有建立 TrGWla和 UE1间的媒体连接，因为要使用优化的媒体路径， 就没必要再建立这段媒体连接了。
实施例三
图 4所示为相应于图 1A的本实施例的流程图，与实施例 1不同的是，在 本实施例中， 由 ALG1来发送 SDP请求， 所述方法主要包括以下步骤：
步骤 401-406, 与图 2中的步骤 201-206相同；
步骤 407、 ALG4根据收到的路径上的各 ALG相关的信息， 判断 ALG4 与 ALG1间存在一个更短路径， 于是生成要添加到 SDP响应中的指示信息， 以指示希望 ALG1建立与 ALG4间的优化媒体路径；
在本实施例中， 由于由 ALG1发起新会话， 因此指示信息中可以不携带 关联标识， 但要携带 ALG4的相关信息， 比如 ALG4的地址信息。
步骤 408~411、 与图 2中的步骤 208~211相同；
步骤 412、 ALG1控制 TrGWlb分配用于连接远端的媒体资源， ALG1以 TrGWlb用于连接远端的媒体资源信息生成 SDP请求， 并发送该 SDP请求， 比如通过 SIP信令的 INVITE请求， 通过该 SIP请求的消息体携带该 SDP请 求来发送， 请求的目标从指示信息中包含的 ALG4相关的信息中获得；
步骤 411与步骤 412的执行顺序不限。
步骤 413、 SDP请求到达 ALG5 , ALG5控制媒体网关 TrGW5使用 SDP 请求中的媒体资源信息， 并分配用于连接远端的媒体资源， ALG5以 TrGW5 用于连接远端的媒体资源信息生成 SDP请求，并发送该 SDP请求， 比如通过 转发 SIP信令携带该 SDP响应来转发；
步骤 414、 SDP请求到达 ALG4, ALG4控制 TrGW4b使用该 SDP请求 中的媒体资源信息， 并分配用于连接近端的媒体资源， ALG4以 TrGW4b用 于连接近端的媒体资源信息生成 SDP响应，并发送该 SDP响应， 比如通过发 送 SIP信令的 "200 OK"回应，通过该回应的消息体携带该 SDP响应来发送； 至此， TrGW4b与 TrGW5间的媒体连接建立起来了。
步骤 415、 SDP响应到达 ALG5 , ALG5控制 TrGW5使用该 SDP响应中 的媒体资源信息， 并分配用于连接近端的媒体资源， ALG5以 TrGW5用于连 接近端的媒体资源信息生成 SDP响应， 并发送该 SDP响应， 比如通过转发 SIP信令携带该 SDP响应来转发， SDP响应到达 ALG1 , ALG1控制 TrGWlb 使用该 SDP响应中的媒体资源信息；
至此， TrGW5与 TrGWlb间的媒体连接建立起来了。
步骤 416~418、 与图 2中的步骤 216~218相同；
步骤 419、 可以在步骤 413之后， 也可在步骤 418之后， 如果 TrGW4b 与 TrGW4a不同，则 ALG4控制 TrGW4b分配用于连接远端的媒体资源， ALG4 以 TrGW4b用于连接远端的媒体资源信息生成 SDP请求， 并发送该 SDP请 求， 比如， 如果在步骤 418之后， 可通过转发 SIP信令携带该 SDP请求来转 发， 或如果在步骤 413之后， 通过发送 SIP信令的 relNVITE (重邀请 )请求， 通过该 SIP请求的消息体携带该 SDP请求来发送；
步骤 420、 SDP请求到达 UE2, UE2使用该 SDP请求中的媒体资源， 并 发送 SDP响应以携带 UE2的媒体资源信息， 比如发送 SIP信令的 "200 OK" 回应， 通过该 SIP回应的消息体携带该 SDP响应来发送；
步骤 421、 可选的， 在步骤 418之后， 或者可在步骤 420之后， ALG4沿 原会话路径发送新的 SDP响应， 其中携带无效的媒体资源信息以指示该媒体 路径上的资源已经释放， 比如， 如果在步骤 420之后， 可通过转发 SIP信令 携带该 SDP响应来转发， 或如果在步骤 418之后， 通过发送 SIP信令的 "200 OK" 回应 , 通过该 SIP回应的消息体携带该 SDP响应来发送；
步骤 422、 SDP响应到达 ALG3 , ALG3转发该 SDP响应， 比如通过转发 SIP信令携带该 SDP响应来转发；
步骤 423、 SDP响应到达 ALG2 , ALG2转发该 SDP响应， 比如通过转发
SIP信令携带该 SDP响应来转发；
至此，优化的媒体路径便建立起来，媒体路径为 UE1、 TrGWlb、 TrGW5、 TrGW4b、 UE2, 原媒体路径 TrGWla、 TrGW2、 TrGW3、 TrGW4a、 UE2通 过步骤 416~423 被释放， 其中 TrGW4a与 UE2 间的媒体连接是通过步骤 419-420被更新为 TrGW4b与 UE2间的媒体连接。 本实施例原媒体路径建立 过程中没有建立 TrGWla和 UE1间的媒体连接，因为要使用优化的媒体路径， 就没必要再建立这段媒体连接了。
尽管为示例目的， 已经公开了本发明的优选实施例， 本领域的技术人员 将意识到各种改进、 增加和取代也是可能的， 因此， 本发明的范围应当不限 于上述实施例。
本领域普通技术人员可以理解上述方法中的全部或部分步骤可通过程序 来指令相关硬件完成， 所述程序可以存储于计算机可读存储介质中， 如只读 存储器、 磁盘或光盘等。 可选地， 上述实施例的全部或部分步骤也可以使用 一个或多个集成电路来实现。 相应地， 上述实施例中的各模块 /单元可以釆用 硬件的形式实现， 也可以釆用软件功能模块的形式实现。 本发明不限制于任 何特定形式的硬件和软件的结合。
工业实用性
釆用本发明所述方法和信令网关， 能够有效缩短呼叫建立时间， 为用户 提供更好的使用体验。

Claims

权 利 要 求 书
1、 一种优化媒体路径的建立方法， 用于 IP多媒体子系统（IMS ) 网络 中， 所述方法包括：
转发会话描述协议（SDP )请求与响应的过程中， 在接收到第一会话的 SDP响应时，第一信令网关（ALG )判断与第二 ALG间存在优化的媒体路径， 则在发送第一会话的 SDP响应时， 并在发送的 SDP响应中携带指示信息； 所述第一 ALG发送以所述第二 ALG为目标的 SDP请求； 以及
所述第二 ALG收到携带所述指示信息的第一会话的 SDP响应后， 或者 在收到以所述第二 ALG为目标的 SDP请求和携带所述指示信息的第一会话 的 SDP响应后， 发送第一会话的 SDP响应。
2、 如权利要求 1所述的方法， 其中，
所述指示信息用来指示与所述第二 ALG间建立优化媒体路径，所述第一 ALG和第二 ALG发送的第一会话的 SDP响应中还携带用于建立优化媒体路 径的资源信息。
3、 如权利要求 1所述的方法， 其中，
所述第一会话的 SDP响应中的指示信息中携带有关联标识， 在所述第一 ALG发送以所述第二 ALG为目标的 SDP请求的步骤中，在携带所述 SDP请 求的会话初始协议（SIP ) 消息中携带所述关联标识。
4、 如权利要求 1所述的方法， 该方法还包括：
所述第二 ALG收到以所述第二 ALG为目标的 SDP请求后， 发起第一会 话媒体路径资源的释放。
5、 如权利要求 1所述的方法， 其中，
所述指示信息中包含与第二 ALG相关的信息。
6、 一种优化媒体路径的建立方法， 用于 IP多媒体子系统（IMS ) 网络 中， 所述方法包括：
转发会话描述协议（SDP )请求与响应的过程中， 在接收到第一会话的 SDP响应时，第一信令网关（ALG )判断与第二 ALG间存在优化的媒体路径， 则在发送第一会话的 SDP响应时， 在所述发送的 SDP响应中携带指示信息； 以及
所述第二 ALG收到携带所述指示信息的第一会话的 SDP响应后， 以所 述第一 ALG为目标发送 SDP请求。
7、 如权利要求 6所述的方法，其中， 所述指示信息用来指示与所述第二
ALG间建立优化媒体路径， 该方法还包括：
所述第二 ALG收到携带所述指示信息的第一会话的 SDP响应后， 发送 第一会话的 SDP响应，所述发送的 SDP响应携带用于建立优化媒体路径的资 源信息。
8、 如权利要求 6所述的方法， 该方法还包括：
所述第一 ALG收到以本 ALG为目标的 SDP请求后，发送第二会话的 SDP 响应； 所述第二 ALG收到第二会话的 SDP响应后， 发起第一会话媒体路径 资源的释放。
9、 如权利要求 5所述的方法， 其中，
所述指示信息中包含与所述第一 ALG相关的信息和所述第二 ALG相关 的信息。
10、 一种建立优化媒体路径的信令网关 （ALG ) ， 其包括： 切出模块和 切入模块， 其中：
所述切出模块设置为： 在转发会话描述协议（SDP )请求与响应的过程 中， 在接收到第一会话的 SDP响应时， 判断本 ALG与第一会话媒体路径上 的另一 ALG间存在优化的媒体路径， 则在发送第一会话的 SDP响应时， 在 发送的 SDP响应中携带指示信息； 以及发送以所述另一 ALG为目标的 SDP 请求；
所述切入模块设置为：在收到携带与本 ALG相关的指示信息的第一会话 的 SDP响应后，或者在收到以本 ALG为目标的 SDP请求和携带与本 ALG相 关的指示信息的第一会话的 SDP响应后， 发送第一会话的 SDP响应。
11、 如权利要求 10所述的 ALG, 其中， 所述切出模块转发的第一会话 的 SDP响应和所述 SDP请求中都携带关联标识。
12、 如权利要求 10所述的 ALG, 其中， 所述切出模块和切入模块发送 的第一会话的 SDP响应还携带用于建立优化媒体路径的资源信息。
13、 如权利要求 10所述的 ALG, 该 ALG还包括中间模块， 其设置为： 接收到携带与本 ALG无关的第一会话的 SDP响应后，发送携带所述与本 ALG 无关的指示信息的第一会话的 SDP响应。
14、 一种建立优化媒体路径的信令网关 （ALG ) ， 其包括： 切出模块和 切入模块， 其中：
所述切出模块设置为： 在转发会话描述协议（SDP )请求与响应的过程 中， 在接收到第一会话的 SDP 响应时， 判断与第一会话媒体路径上的另一 ALG 间存在优化的媒体路径， 则在发送第一会话的 SDP响应时， 在发送的 SDP响应中携带指示信息；
所述切入模块设置为：在收到携带与本 ALG相关的指示信息的第一会话 的 SDP响应后，以指示信息中指示的与本 ALG间存在优化的媒体路径的 ALG 为目标发送 SDP请求。
15、 如权利要求 14所述的 ALG, 其中， 所述切入模块还设置为： 在收 到携带与本 ALG相关的指示信息的第一会话的 SDP响应后， 发送第一会话 的 SDP响应， 发送的 SDP响应；
所述切出模块和切入模块发送的第一会话的 SDP响应还携带用于建立优 化媒体路径的资源信息。
16、 如权利要求 14所述的 ALG, 其中，
所述切出模块还设置为： 收到以本 ALG为目标的 SDP请求后， 发送第 二会话的 SDP响应；
所述切入模块还设置为： 在接收到第二会话的 SDP响应后， 发起第一会 话媒体路径资源的释放。
17、 如权利要求 14所述的 ALG, 该 ALG还包括中间模块， 其设置为： 接收到携带与本 ALG无关的指示信息的第一会话的 SDP响应后， 发送携带 所述与本 ALG无关的指示信息的第一会话的 SDP响应。
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EP2485444B1 (en) 2019-11-20
CN102056327B (zh) 2014-03-12
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US20120213221A1 (en) 2012-08-23
EP2485444A4 (en) 2017-05-31
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US9281964B2 (en) 2016-03-08
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